Here's a business-lounge scary story. In 1994, Warner Bros was feeling very pleased with itself. It had just finalised a joint venture with the Chinese government to bring the splendours of multiplex cinema to the country. And the terms were good: a 70/30 profit split in favour of the Americans. Building began, but several months later, strange tidings arrived at Warner HQ. The arrangement had been reviewed: still favouring Warner, but now to the tune of 51/49. There was confusion and disbelief in California, but work continued. The eighth cinema was ready when the inevitable happened: the Chinese authorities decided that foreign companies could not own cinemas. The split was arbitrarily reversed 49/51, leaving Beijing with its hands on the curtain cords of several million dollars' worth of chipper new multiplexes.

The moral? China has "opened up" before. This summer, an opening appeared again. Two Hollywood companies looked to have cracked it: signing production agreements with Chinese companies allowing them to bypass the dreaded quota limiting foreign film releases to 20 a year. Relativity Media, Ryan Kavanaugh's vibrant mini-studio, got the golden ticket: a partnership with state-owned distributor Huaxia to make "Chinese-based material with global appeal". Legendary Pictures (who have funded many of Warner Bros' bigger recent releases, including 300 and Inception) have teamed up with China's largest private media company, Huayi Brothers, to form Legendary East. The new outfit is going to produce English-language films that package up Chinese culture for a global audience.

The most optimistic view of the split this time is 50/50. The American companies get a peek into the high-walled Chinese playground; China gets an injection of Hollywood storytelling pep, marketing savvy and global distribution that might help its film industry kick on. Despite the endless barrage of coverage declaring the 21st century Beijing-owned, Chinese cinema isn't flourishing, numerically at least. Official figures claim 400 films a year, but the real figure is supposed to be between 50 and 100; putting them on a par with countries like Russia, Denmark and Mexico. Its labyrinthine censorship practices tend to favour stodgy historical epics, like Red Cliff, The Warlords and Confucius, which don't seem likely to satisfy its growing film audience for long: box office boomed by a staggering 60% in 2010, up to $1.5bn.

This might look like a green light for Hollywood. But Screen International's Liz Shackleton had some advice for Legendary and Relativity in a recent article: "If China wants you in, you're in, and if it wants you out, there's not much you can do about it. But even those who are 'in' need to be wary. China has a habit of inviting companies to manufacture in the country, learning all their processes, and then setting off on its own with very successful imitations."

To be blunt, only China has access to the whole rulebook. Some commentators thought the quota would simply be slowly increased by, say, 10 films a year – but this summer's deals look like the Communist party want to play the éminence grise game, and keep things vague. It's understandable that Beijing wants to keep a grip on its own film market, which is as vulnerable to Hollywood as any other country (the US already takes a 50% share with its 20 films); but its plans for Chinese-flavoured mass-market movies also look like the opening moves in a soft-power chess game. Legendary and Relativity need to be aware. It could be a brave new era for them or history could be repeating itself. Typical: all you want is to make movies, and everything gets geopolitical on your ass.

What global box-office stories should we be writing about? How does Hollywood hawk its wares in your country? Let us know in the comments below …